- This article refers to the general concept of alternate realities, for the timeline of the 2009 movie Star Trek see Kelvin timeline, for other specific timelines see listings below.
An alternate reality (which may also be referred to as an alternate quantum reality, alternate timeline or parallel timeline) is a divergent timeline, a distinct branch in any one universe. The terms "alternate universe" or "parallel universe" are sometimes also used to refer to alternate realities, however such usage is inaccurate; a universe is a distinct separate place, divided from other universes by higher dimensions (and may have its own alternate timelines), while an alternate reality is merely a different quantum facet of any one universe, with the same laws of physics, just different histories. (VOY - Myriad Universes novel: Places of Exile)
As understood by quantum theory, any event creates an infinite number of possible outcomes, all of which are played out in alternate quantum realities. Each alternate reality is ordinarily separate from the others, and distinguished by its unique quantum signature. Alternate realities, together with alternate universes (and their own alternate realities), form the multiverse. (TNG episode: "Parallels"; VOY - Myriad Universes novel: Places of Exile; TNG novel: I, Q)
Knowledge of other realities
In theory there are an infinite number of realities, ever branching with one for every infinite outcome. As of the 2370s, Starfleet had records of 285,000 different quantum realities. (TNG episode: "Parallels"; ST reference: The Starfleet Survival Guide)
Other cultures have exhibited far greater knowledge and even control of the timelines. The Sphere Builders had technology which allowed them to examine timelines. When they were manipulating the Xindi into trying to destroy Earth in the 2150s, they could see when the actions of the starship Enterprise were generating more timelines with unfavorable outcomes for themselves and acted to try and alter the flow of the events to something they preferred. (ENT episodes: "Azati Prime", "Zero Hour")
El-Aurians seemed had an innate ability to read timelines. In at least two different alternate timelines, both of which, for different reasons, had seen the Federation and the Klingon Empire go to war, Guinan provided counsel to Jean-Luc Picard as she was concerned that things were not as they should be. She could sense there was another more peaceful timeline and sought to have actions taken to change the timelines to avert the wars. (TNG episode: "Yesterday's Enterprise"; TNG - The Last Generation comic: "Do Not Close Your Eyes")
In the 22nd century, the Krenim scientist Annorax created the Krenim temporal weapon ship, armed with a weapon which could wipe entire civilizations out of time, and in doing so create new divergent timelines. Over the next two centuries, Annorax made alteration after alteration, carefully monitoring the timelines to try and restore the Krenim Imperium to greatness. (VOY episode: "Year of Hell")
In 2376, Iliana Ghemor, driven mad by years of captivity and believing that she was Kira Nerys, devised a plan to travel to as many alternate realities as she could access and kill all other Kira Nerys, determined that she would be the only one. (DS9 novel: Warpath)
By the 29th century Starfleet had an advanced knowledge of time travel and alternate realities and employed temporal agents to monitor them. One agent, Captain Braxton became aware of massive event that literally destroyed the galaxy; he could not determine what caused the event due to the temporal chaos surrounding it, but could see that only timeline in which the Federation no longer existed survived it. In trying to undo the catastrophe and save as many timelines as possible Braxton made alterations through time, including attempting to sabotage the Khitomer Accords. (TNG - The Last Generation comic: "The End of History")
22nd century alternate timelines
23rd century alternate timelines
In the 2250s and 2260s, Christopher Pike commanded the UESS Enterprise in a timeline in which United Earth became isolationist following Terra Prime's successful attack on the Coalition of Planets conference in 2155. (TOS - Myriad Universes novel: A Less Perfect Union)
In 2267, Doctor Leonard McCoy traveled through the Guardian of Forever to 1930, creating a timeline in which Edith Keeler did not die in a traffic accident and the Nazis won World War II and eventually conquered Earth. (TOS episode: "The City on the Edge of Forever", TOS novel: Provenance of Shadows)
- See mirror universe article for other crossovers with the main mirror universe and alternate mirror universes.
Later that year, Professor Omen invented the Aleph, a device which could transport objects into other universes. One Aleph transported the Enterprise to a universe in which space was ruled by the Klingees. (TOS novel: The Starship Trap)
In 2270, the crew of the USS Enterprise discovered that the Klingon developed technology that opened a doorway into Otherdimensional space, so as to expand their territory and circumvent the Organian Peace Treaty. The portal created by the Klingons led to a universe, in the vicinity of Earth, where man had regressed to mute animals whilst intelligent apes ruled as the dominant species. (TOS comic: "The Primate Directive")
Later that year, Dr. Georges Mordreaux conducted time travel experiments that resulted in alternate timelines, including one in which his insane future self killed Kirk with a spiderweb gun. (TOS novel: The Entropy Effect)
24th century alternate timelines
In or before 2364, a timeline was created where Tasha Yar survived the attack of the lifeform Armus. By the year 2368, Yar held the rank of lieutenant. However, in that same timeline, Jean-Luc Picard was killed during the Battle of Wolf 359 in 2367. (TNG novel: Headlong Flight)
In 2366, a timeline was created in which the removal of the USS Enterprise-C from 2344 resulted in war between the Federation and the Klingons. The Tasha Yar of this timeline joined the crew of the Enterprise-C, and later became the mother of Sela. (TNG episode: "Yesterday's Enterprise")
In at least two timelines, the Borg Incursion of 2366-2367 was successful and Earth was assimilated by the Borg. (TNG comic: "The Worst of Both Worlds"; TNG short story: "Civil Disobedience") In another, by 2371, the Borg occupation had spread as far as the Bajor system. (DS9 comic: "The Looking Glass War")
In 2369, Jean-Luc Picard, with the aid of Q, created a timeline in which he did not get into a fight with a group of Nausicaans in his youth and, consequently, never assumed command of the Enterprise-D. In that year, he was a lieutenant junior grade serving in the ship's stellar cartography department. (TNG episode: "Tapestry")
In 2370, Montgomery Scott traveled back to 2293 and rescued Kirk from his apparent death on the Enterprise-B, thus creating a timeline in which the Borg invasion of 2063 was successful. (ST novel: Engines of Destiny)
In 2371, members of the crew of Deep Space 9 accidentally created a timeline in which the social reforms that followed the Bell Riots never occurred. Consequently, neither United Earth nor the United Federation of Planets ever existed while the Romulan Star Empire was able to expand its territory to Alpha Centauri. (DS9 episodes: "Past Tense, Part I", "Past Tense, Part II")
Later that year, while Kirk lay dying on Veridian III, the Organians showed him a timeline in which he had resigned from Starfleet following his initial encounter with the Guardian of Forever. (TOS short story: "Reflections")
Later that year, the removal of Benjamin Sisko from normal space-time created an alternate timeline in which Jake Sisko spent the rest of his life trying to get his father back. In this timeline, the Federation-Klingon War intensified following Captain Sisko's disappearance, resulting in the Federation's withdrawal from Deep Space 9 and the existence of poor relations between the two former allies well into the 25th century. Furthermore, Jadzia Dax was still alive in 2422 and the Dominion War never took place. (DS9 episode: "The Visitor")
Later that year, a timeline was created in which the USS Defiant traveled back in time 200 years and crashed on a planet in the Gamma Quadrant, forcing the crew to colonize it. (DS9 episode: "Children of Time")
Later that year, Wesley Crusher created a timeline in which the Battle of the Border was fought between the Federation and the Cardassian Union in late 2370. (TNG short story: "Gods, Fate, and Fractals")
In one timeline, Captain Braxton believed that Voyager would be responsible for accidentally destroying Earth in the 29th century, and attempted to prevent this by destroying Voyager first. (VOY episode: "Future's End")
That year also saw the creation of a timeline in which the opening of a second wormhole in the Bajoran system destroyed Deep Space 9. (DS9 - Millennium novels: The Fall of Terok Nor, The War of the Prophets, Inferno)
In 2375, an attempt to use a quantum slipstream drive to return Voyager to the Alpha Quadrant created a timeline in which the ship crashed on an ice planet, killing everyone aboard and leaving Chakotay and Harry Kim as the only surviving crewmembers. (VOY episode: "Timeless")
In 2376, an alternate timeline was created in which the Borg successfully assimilated Ambassador Spock, leading to the destruction of Starfleet Command and the assimilation of Earth. (TNG video game: Armada)
In a timeline in which Khan Noonien Singh won the Eugenics Wars and Humans underwent genetic engineering en masse, Princeps Julian Bashir commanded the Khanate of Earth starship Defiance during the late 24th century. (DS9 - Myriad Universes novel: Seeds of Dissent)
In a timeline where Dulmur and Lucsly were removed from 2384, the Temporal Defense Grid was not developed. The Federation's Temporal Intervention Agency emerged as an aggressive faction in the Temporal Cold War, and approached supremacy by the year 3055. (DTI eBook: The Collectors)
25th century alternate timelines
When the Iconian War raged in 2410, the desperate Alpha Quadrant Alliance built a Annorax-class temporal weapon ship to change the timeline in the AQA's favor. Before the ship, the KIS Annorax, was launched, the AQA ran simulations, including on the holodeck, of potential timelines. (STO - The Iconian War mission: "Butterfly Effect") The simulations yielded the following timelines:
- Removing the Iconians directly delayed the development of warp drive in the Alpha Quadrant by about 50,000 years.
- In one version related to this timeline, the Dewans developed warp engines and rose to power. They conquered most of the Beta Quadrant but a forced back by Vulcans who never embraced Surakian logic. The Vulcan Star Empire enslaved what in the primary timeline was Federation and Klingon space. Because the Hur'q never developed warp drive at all, Qo'noS was not invaded. When the Vulcans encountered the Klingons in the 22nd century, they found them a primitive farmer culture with some advances in epic poetry. By the present day of the simulation, the Vulcan Star Empire was embroiled in a to-the-death-struggle with the Dominion.
- Because removing the Iconians would have proved disastrous, Alteration Alpha sought to delay their invasion by 700 years, until the 32nd century. In this timeline, the Klingons were not unified, and embroiled with a war with the Romulans and the Federation. The Alpha Quadrant powers were so weakened that the Dominion took local space in a brutal assault that left major worlds in ashes. On stardate 87319.0, they reached Earth.
- The goal of Alteration Beta was to reduce the powerbase of the Iconian Empire by preventing Voyager from rediscovering the Vaadwaur in 2377. In the simulation, the Iconians chose the Hierarchy as their servitor race instead, and dispatch the Elachi to aid them in the conquest of the Delta Quadrant. Inter-species conflicts were exacerbated, and by stardate 87234.5 the Federation had been unable to form the Delta Alliance, preventing the Allies from resisting the Hierarchy.
- In Alteration Gamma, a meteor was redirected to destroy a star chart on Denius III, preventing Captain Donald Varley from rediscovering Iconia in 2365. This delayed gaining the attention of the Iconians until another Iconian gateway was discovered only a few years later.
- When the KIS Annorax was deployed to change the timeline, the simulation showed that Romulus was not destroyed in the Hobus event. In reality, the timeline changed so that the Borg Collective conquered the Romulan Star Empire and had assimilated Romulus.
- This timeline was changed further by erasing the Borg transwarp gate leading to the Beta Quadrant. As a result, the Tuterians were assimilated by the Borg because they failed to develop Solanae technology in time. The surviving Tuterians fled into another plane of existing, and evolved into the vengeful Sphere Builders. (STO - The Iconian War mission: "Butterfly Effect")
Also in 2410, the Federation Temporal Agency from the 31st century recruited an Alpha Quadrant Alliance vessel to protect the timeline. During a joint mission between the AQA and the Starfleet of the Kelvin timeline, the Alliance learned of timelines that had been experimented upon by the Sphere Builders:
- Experiment #2674: The failure to contain transdimensional rift in this timeline led to universal instability, and eventually entropic acceleration. The Sphere Builders terminated the project because galactic habitability dropped to zero, and life-signs were minimal.
- Experiment #3331: The Delphic Expanse grew at a rate satisfactory for the Sphere Builders, until it was discovered by the Iconian-Dominion Alliance. Due to the IDA's intense resistance, the Sphere Builders decimated their core systems with "micro-Expanses". The IDA desperation assault in subspace led to entropic breakdown, culminating in universal disruption. The project was terminated because zero galactic habitable spaces were detected and life-signs remained indeterminate.
- Experiment #4472: The Delphic Expanse increased the Sphere Builder habitability and showed a projected growth rate of 500%. Local resistance chiefly came from the realm's Federation The Sphere Builders deployed Klingon proxy forces to keep them at bay. (STO - Yesterday's War mission: "Terminal Expanse")
26th century alternate timelines
The Battle of Procyon V was a focal point of temporal incursions from the 23rd to the 31st century. Captain Pavel Chekov led the mission to destroy the command sphere from the USS Enterprise. With each successful destruction of the sphere, the increasingly desperate Sphere Builders changed the timeline to bring in more of their allies. Timot Danlen provided temporal assistance, and the combined Federation fleet defeated the incoming waves of Sphere Builders, Terran Empire, Krenim Temporal Liberation Front, Na'kuhl, and Vorgons, destroying the command sphere and closing all temporal portals. With few exceptions, the forces then returned to their respective home eras. (STO - Agents of Yesterday mission: "The Battle of Procyon V") In one version, Danlen brought Jonathan Archer from the 22nd century to witness the battle. (ENT episode: "Azati Prime")
The majority of Star Trek stories take place in "prime reality", a singular timeline which runs from the present day through to all the Star Trek series. The prime reality has generated numerous alternate timelines, though these normally are only explored for the duration of one story. One major exception is the "mirror universe", which has been developed in multiple stories across multiple series (so much so in fact that a number of alternate mirror universes have even been seen). The 2009 movie Star Trek saw a significant movement in the Star Trek universe, with the film establishing a new alternate reality, which rather than being "repaired" back to the prime universe has become the new leading edge of the franchise, with new movies to be set in the continuation of this timeline rather than the original prime timeline. Meanwhile stories from across the franchise continue to be told in both the prime and new timeline, and in the Myriad Universes series even in other alternate timelines.
In his annotations for Places of Exile, Christopher L. Bennett postulates a rationalization for why divergent timelines, even centuries after the point of divergence, manage to generate the same characters, settings and scenarios, even when the same settings recurring so similarly are so improbable: Bennett suggests that because a being in a different timeline is merely one outcome for the same matter that "the physical connection across different timelines means that there can be a sort of quantum resonance: the shared "inertia" of different quantum facets of the same being causes their lives -- and their genetics -- to develop along similar lines"